I forgot to comment on "read fan switch" which I think was probably supposed to be "head fan switch?"

The big difference that lets a system designed for R134a work as well as a system designed for R12 is the size of the condenser. I'm guessing that by changing the fan switch so that the auxilliary electric fan comes in sooner he somewhat compensated for the '90 model's smaller condenser. It sounds like he is knowledgeable and conscientious.

Travis